Pfizer shot passes test in real world

A real-world test of Pfizer’s COVID-19 vaccine in more than half a million people confirms it’s very effective at preventing serious illness or death, even after one dose.

Wednesday’s published results, from a mass vaccination campaign in Israel, give strong reassurance that the benefits seen in smaller, limited testing persisted when the vaccine was used much more widely in a general population with various ages and health conditions.

“This is the kind of vaccine that gives us hope that herd immunity may be possible,” said Dr. Raina MacIntyre, a professor of biosecurity at the University of New South Wales in Sydney.

The vaccine was 92 percent effective at preventing severe disease after two shots and 62 percent after one. Its estimated effectiveness for preventing death was 72 percent two to three weeks after the first shot, a rate that may improve as immunity builds over time.

And it seemed as effective in folks over 70 as in younger people.

“This is immensely reassuring … better than I would have guessed,” said Dr. Gregory Poland of the Mayo Clinic.

Vanderbilt University’s Dr. Buddy Creech agreed: “Even after one dose we can see very high effectiveness in prevention of death.”

Both doctors also said the new results may boost consideration of delaying the second shot, as the United Kingdom is trying, or giving one dose instead of two to people who already have had COVID-19, as France is doing, to stretch limited supplies.

“I would rather see 100 million people have one dose than to see 50 million people have two doses,” Creech said. “I see a lot of encouragement on one dose” in the results from Israel.

Researchers compared nearly 600,000 people 16 and older in Israel’s largest health care organization who were given shots in December or January to an equal number of people of similar age, sex and health who didn’t receive a vaccine. None of the participants had previously tested positive for the virus.

The vaccine was estimated to be 57 percent effective at preventing any symptoms of COVID-19 two to three weeks after the first dose, and 94 percent a week or more after the second dose.